System for checking seals in a packaging plant

Abstract

The seal of a package comprising a cup containing a liquid or semiliquid substance and having a rim to which a flexible cover is sealed is checked by simultaneously monitoring the position of the cover, inwardly elastically deflecting at least one of the walls of the cup so that the disk is bulged outward only when the cup is sealed, and generating an output based on the monitored position of the disk when the disk is bulged outward. The cup is held substantially stationary while monitoring the cover-disk position and inwardly deflecting the one wall, although normally diametrically opposite side walls are simultaneously and oppositely inwardly deflected. The position of the cover disk is monitored by pressing a bumper against it resiliently and detecting movement of the bumper.

I claim: 
     
       1. In a packaging process where a succession of vessels are filled and each filled vessel has a rim to which is sealed a flexible cover disk, a method of checking the package seal comprising the steps of simultaneously: (a) supporting said succession of filled vessels by respective rims so that bodies of the filled vessels hang freely downwardly below supported portions of the vessels;   (b) advancing said vessels suspended at said portions in succession to a checking location; and   (c) at said location and in succession for the vessels monitoring the position of each cover disk of the respective vessels, inwardly elastically deflecting at least one of the walls of each vessel at the body thereof below the respective supported position during monitoring of the position of the respective cover disk and thereby decreasing the volume defined within the vessel, whereby the disk thereof is bulged outward above the respective supported location only when the vessel is sealed, and   generating an output based on the monitored position of the disk the respective disk is bulged outward.   
     
     
       2. The seal-checking method defined in claim 1, further comprising the step of holding the vessel substantially stationary while monitoring the cover-disk position and inwardly deflecting the one wall.   
     
     
       3. The seal-checking method defined in claim 2 wherein diametrically opposite side walls are simultaneously and oppositely inwardly deflected. 
     
     
       4. The seal-checking method defined in claim 2 wherein the position of the cover disk is monitored by pressing a bumper against it resiliently and detecting movement of the bumper. 
     
     
       5. In a packaging system wherein a filled vessel has a rim to which is sealed a flexible cover disk, an apparatus for checking the package seal and comprising: a conveyor having means suspending said vessel at a supported portion adjacent said rim so that a body of said vessel is freely suspended below said portion, said conveyor being displaceable for positioning the vessel in a checking station with said body of the vessel freely suspended below said supported portion;   means at the station for monitoring the position of the cover disk;   means including at least one pusher for inwardly elastically deflecting at least one of the walls of said body of the vessel below said supported portion and thereby decreasing the volume defined within the vessel, whereby the disk bulges outward above said supported portion when the vessel is sealed but does not when the vessel is leaky; and   control means connected to the pusher means for generating an output based on the monitored position of the disk when the disk bulges outward.   
     
     
       6. The seal-checking apparatus defined in claim 5 wherein the conveyor means includes a conveyor element formed with a succession of seats extending in a horizontal transport direction of the conveyor means and each adapted to receive a respective vessel; and   means for displacing the element with the seats passing successively through the checking station in the transport direction.   
     
     
       7. The seal-checking apparatus defined in claim 6 wherein the vessel has a rim that is held horizontally by the seat in the station and two such pushers move oppositely into opposite side walls of the vessel. 
     
     
       8. The seal-checking apparatus defined in claim 7 wherein the transport direction is generally perpendicular to the movement direction of the pushers. 
     
     
       9. The seal-checking apparatus defined in claim 7 wherein each pusher is a horizontal bar. 
     
     
       10. The seal-checking apparatus defined in claim 9 wherein the bars have rounded edges engageable with the vessel. 
     
     
       11. The seal-checking apparatus defined in claim 9 wherein the conveyor element defines a plurality of rows of such seats extending in the transport direction and one such checking apparatus is provided for each such row of seats and forms therefore a slot extending in the transport direction, each pair of pusher bars flanking the respective slot. 
     
     
       12. The seal-checking apparatus defined in claim 11 wherein the pusher means includes respective parallelogrammatic linkages carrying the bars. 
     
     
       13. The seal-checking apparatus defined in claim 12 wherein each such parallelogrammatic linkage has a link fixed to a respective link of the linkage of the adjacent slot, whereby the bars move synchronously. 
     
     
       14. The seal-checking apparatus defined in claim 13 wherein the pusher means includes a link pivoted to and interconnecting all the parallelogrammatic linkages for joint synchronous movement. 
     
     
       15. The seal-checking apparatus defined in claim 14 wherein the pusher means includes a single actuator connected to one of the linkages and through the link to all the other linkages for joint operation of all the pusher bars. 
     
     
       16. The seal-checking apparatus defined in claim 11 wherein each pusher bar is long enough to engage the containers of at least two succeeding seats in the same seat row of the conveyor element. 
     
     
       17. In a packaging system wherein a filled vessel has a rim to which is sealed a flexible cover disk, an apparatus for checking the package seal and comprising: a conveyor having means suspending said vessel at a supported portion adjacent said rim so that a body of said vessel is freely suspended below said portion, said conveyor being displaceable for positioning the vessel in a checking station with said body of the vessel freely suspended below said supported portion;   means at the station for monitoring the position of the cover disk;   means including at least one pusher for inwardly elastically deflecting at least one of the walls of said body of the vessel below said supported portion and thereby decreasing the volume defined within the vessel, whereby the disk bulges outward above said supported portion when the vessel is sealed but does not when the vessel is leaky;   control means connected to the pusher means for generating an output based on the monitored position of the disk when the disk bulges outward, said conveyor including: a conveyor element formed with a succession of seats extending in a horizontal transport direction of the conveyor means and each adapted to receive a respective vessel, and   means for displacing the element with the seats passing successively through the checking station in the transport direction;     a vertically movable support at the station and carrying the pusher for movement between an upper position unengageable with the cover of a vessel in the station and a lower position engageable therewith;   a substantially stationary support under the conveyor element in the station; and   a hold-down element on the support engageable only in the lower position of the support with the element to hold it down against the support.